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sábado, 27 de abril de 2013

Learning from FMD outbreaks

As the United States plans and prepares for the possibility of an outbreak of foot and mouth disease (FMD), we have the benefit of knowledge gained from outbreaks around the world in recent years. During last week’s annual conference of the National Institute for Animal Agriculture, University of California-Davis veterinarian Pam Hullinger described what went right and what might have been done differently in several FMD outbreaks.

Taiwan, 1997

The strain involved in this outbreak only caused clinical signs in pigs, which resulted in early misdiagnosis. Delays in detecting the virus, a heavy concentration of hogs in the area, slow implementation of vaccinations and a shortage of vaccine once implemented resulted in a large impact. The country killed 74 million hogs, 38 percent of the total population, from over 6,000 farms, resulting in $2 billion per year in export losses alone.

United Kingdom, 2001

The index farm did not report problems as they appeared, and ended up shipping infected sheep well after the outbreak began. Early in the outbreak, farmers did not have adequate information and biosecurity practices were inadequate. The country depopulated 10,000 farms, resulting in economic disruptions that continue today. UK officials depopulated uninfected farms adjacent to infected farms, a practice Hullenger says probably was not necessary.

Uruguay, 2001

In contrast to the UK, Uruguay culled very few animals. Animal health officials quickly recognized the rapidly spreading outbreak, which infected herds on 28 farms in the first five days. They initially implemented a “ring-vaccination” program, vaccinating animals in areas surrounding the outbreak, but within seven days, with 131 farms infected, switched to a national vaccination program. In cooperation with the government, farmers administered two rounds of over 12 million doses of the vaccine to susceptible animals across the country. Only 7,000 animals were destroyed, and Uruguay’s beef exports resumed within one year. The country was rated FMD-free by May 2003, but the national vaccination program continues today.

United Kingdom, 2007

A relatively small outbreak occurred with the virus apparently escaped from a vaccine-manufacturing facility. The disease was well established in a small herd before it was detected, but there was little movement of animals from the site and the outbreak was quickly contained.

Japan, 2010

The outbreak began in a small cattle herd and spread to 10 farms before being detected. Two months after detection, the government implemented a vaccination program, with animal-health officials controlling and administering the vaccine. Slow detection and quarantine resulted in culling of 200,000 animals on 300 farms.

South Korea, 2011

The virus was detected in swine in October 2010, and the strain was difficult to detect in cattle and farmed deer. The country implemented culling, quarantines and 2,500 disinfection stations. Inhumane culling practices made international news in some cases. The country began emergency vaccinations in January 2011, distributing 30 million doses of vaccines. Widespread culling resulted in food shortages and high food prices in South Korea.

Bulgaria and Turkey, 2011

Animal health officials detected FMD in a hunter-killed wild boar along the border between Bulgaria and Turkey. Testing of wildlife in the area suggests a low rate of transmission. Hullinger says this and other research indicate wild pigs, deer or other wildlife probably would not play a major role in spreading the virus in a U.S. outbreak.

Israel, 2011

Israel routinely vaccinates livestock for six strains of the FMD serotype that occurs there. The strain in this outbreak was similar to three strains in the vaccine, but not an exact match. Virtually all infected animals had been vaccinated, but those vaccinated within two weeks prior to the outbreak did not show evidence of the virus. Hullinger says this experience shows there is a lot yet to learn about vaccinating for FMD.

Hullinger lists these common threads that influence success in controlling outbreaks:

Early recognition, detection and reporting

Effective biosecurity in response to the disease and good routine biosecurity overall

When necessary, early implementation of vaccination

We now have the benefits of better understanding of the disease and better diagnostics than in the past, Hullinger says. We also face challenges due to the high concentration of livestock in some areas of the United States and the high rate of movement of livestock through markets and between operations. Past experience shows the value of investing in preparedness.